I have a '77 2375 with a neck that is very similar to that shown. In fact, with the exception of the headstock shape, its identical. It has no truss cover or plug because the neck has a maple cap fingerboard. The truss adjuster is at the neck heal and the truss rod was obviously installed from the top before the fingerboard was glued down.

What about the headstock? It looks as if the part with the Ibanez logo has a different color. So could it be that this part once belonged to an ibanez and that it is now glued on a Chinese Squier or worse? Or is it just that the first contributions of this thread got me in a suspicious state of mind?